Problem: Express your answer in scientific notation. $8.8 \cdot 10^7 + 3.1 \cdot 10^8 = $
$\phantom{=} 8.8 \cdot 10^7 + {3.1 \cdot 10^8}$ $=8.8 \cdot 10^{7} + {31\cdot10^{7} }$ $= (8.8+31)\cdot10^{7}$ $=39.8\cdot10^{7}$ $=3.98\cdot10^8$